Background: It has been reported coronary vasa vasorum is associated with plaque vulnerability, and low-echoic structures in grayscale intravascular ultrasound (IVUS) are consistent pathologically with vasa vasorum. However, the association of low-echoic structures with plaque composition and no-reflow phenomenon during percutaneous coronary intervention (PCI) is unclear.
Objectives: We investigated plaque composition in virtual histology IVUS (VH-IVUS) and no-reflow phenomenon during PCI of low-echoic structures.
Methods: This study was conducted on consecutive 93 patients 106 lesions treated by PCI for de novo coronary stenosis at our institution between March 2012 and September 2013, and for which good images were obtained through IVUS studies conducted before the PCI procedure. Low-echoic structure was defined as a small tubular structure exterior to media without a connection to the vessel lumen in ≥3 consecutive cross-sectional IVUS images. Lesions with low-echoic structures were found in 42% (45/106).
Results: Lesions with low-echoic structures had more acute coronary syndrome (ACS) patients (53% [24/45] vs. 20% [12/61], P<0.001), more positive remodeling (49% [22/45] vs. 21% [13/61], P=0.003), more spotty calcification (78% [35/45] vs. 39% [24/61], P<0.001), a large number of VH-IVUS derived thin-cap fibroatheromas (VH-TCFAs) (0.64±0.53 vs. 0.05±0.22, P<0.001), more VH-TCFAs with a baseline plaque burden of 70% or more and minimal luminal area of 4.0 mm2 or less (29% [13/45] vs. 2% [1/61], P<0.001), more frequent no-reflow phenomenon after stent implantation and more final TIMI flow grade 0/1/2 (38% [17/45] vs. 5% [3/61], P<0.001; 9% [4/45] vs. 0% [0/61], P=0.03) than lesions without low-echo structures. The multivariable analysis showed that low-echoic structures was an independent predictor of no-reflow after stent implantation (odds ratio 4.93, 95% CI 1.04–23.35, P=0.04). Number of low-echoic structures in the ACS patients was significantly higher than the SAP patients (1.2±1.1 vs. 0.5±0.9, P=0.002). Number of low-echoic structures in the lesions with VH-TCFAs was significantly higher than the lesions without VH-TCFAs (1.7±1.0 vs. 0.4±0.8, P<0.001)
Conclusions: Lesions with low-echoic structures in grayscale IVUS had high plaque vulnerability with more ACS patients, more positive remolding, more spotty calcification and more VH-TCFAs with large plaque burden and small luminal area, and they had more frequent no-reflow phenomenon during PCI than lesions without low-echoic structures. Low-echoic structures showed the activities of ACS and VH-TCFAs from the fact that ACS patients or lesions with VH-TCFAs had a large number of low-echoic structures.